Method for the production of lamella packets for adjustable steering columns

ABSTRACT

The invention relates to a method for producing lamella packets ( 60, 70 ) of the type normally used in adjustable steering columns in automobiles and which comprise a soft lamella ( 71 ) made of soft sheet metal material and at least one layered hard lamella ( 71 ) placed on top of said material. The lamella ( 71, 74 ) are connected by at least one rivet made of soft lamella ( 71 ). The method is characterized by the use of presses ( 110, 120 ) positioned one after the other. A soft lamella ( 71 ) is formed and stamped out of a strip ( 111 ) of said softer material in the first press ( 110 ) at a rate dictated by the press ( 110 ). Soft lamella ( 71 ) produced in this matter are transported to the second press ( 120 ). At least one hard lamella ( 72, 74 ) is completely formed in a second press ( 120 ) from a band ( 121 ) of harder sheet material and then stamped. Said hard lamella is placed over a soft lamella ( 71 ) and a rivet connection is produced.

TECHNICAL FIELD

The present invention relates to a method for producing lamella packetsof the type normally used in adjustable steering columns in automobiles,which prevent slippage and unintended adjustment of the steering columnby means of a plurality of friction surfaces. The lamella packetscomprise a soft lamella made of a relatively soft sheet metal materialand at least one hard lamella placed thereon and made of a relativelyhard sheet metal material. The lamellae in the packets are joined by atleast one rivet, which is formed, respectively, from the soft lamella.

PRIOR ART

Such lamella packets are known in the art and comprise on the one handpackets with so-called longitudinal lamellae and on the other handpackets with so-called height lamellae. The individual lamellae withinthe packets are spaced apart by a distance corresponding approximatelyto their thickness. One packet of longitudinal lamellae and one packetof height lamellae, respectively, form an associated pair. The twopackets of each pair are then pushed together such that longitudinallamellae and height lamellae alternate in the stack. On their mutualcontact surfaces, the lamellae are in part provided with speciallystructured friction surfaces.

A pair each of the aforementioned lamella packets is arranged on eitherside of a so-called guide box, which holds the bearings for the steeringcolumn. Each longitudinal lamella packet is fixed to the guide box bymeans of fastening eyes, while each height lamella pair is mounted to asupport strap, which in turn is fixed to the chassis, also by means offastening eyes. A tension bolt penetrates the guide box as well as allthe lamellae. For this purpose, guide slots are provided on thelamellae.

The adjustability of the steering column is due to the fact that themutually meshing lamella packets can be displaced as well as pivotedrelative to one another. The displacement or pivoting range is limitedby the length of the aforementioned guide slots in the lamellae. To fixthe steering column in a desired position, the tension bolt is tightenedso as to press together the aforementioned friction surfaces on thelamellae.

It goes without saying that—for a given tension force of the tensionbolt—the resulting total friction force or holding force can becorrelated with the number of lamellae in the lamella packets andadjusted in a simple manner by selecting this number.

To keep the lamellae in the prior art lamella packets spaced at thedesired distance, some of them are provided with a collar that is formedout of the lamellar plane in the area of the aforementioned fasteningeyes. The initially mentioned rivet by which the individual lamellae ofeach packet are held together is also formed by such a collar, which isshaped on one of the two outermost lamellae of each packet—the so-calledsoft lamella—at one of the fastening eyes, to the point where it iscapable of penetrating the corresponding fastening eyes of the remaininglamellae. On the far side of the opposite outermost lamella, this collaris then shaped outwardly around the edge of the fastening eye of thatlamella.

DESCRIPTION OF THE INVENTION

The invention, as described in the claims, defines a manufacturingconcept (method) that permits efficient automatic production andassembly of the lamella packets of the described type.

According to claim 1, this method is characterized, in particular, bythe use of two successive presses. At a rate defined by the first press

a soft lamella is completely formed and stamped from a strip of thesofter sheet metal material in the first press,

a soft lamella thus produced is transported to the second press,

at least one hard lamella is completely formed and stamped from a stripof the harder sheet metal material and placed over a soft lamella in thesecond press, and the riveted connection is produced.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in greater detail by means of anexemplary embodiment with reference to the drawing in which

FIG. 1 shows the core piece of an adjustable steering column in anautomobile with a packet of longitudinal lamellae and a packet of heightlamellae,

FIG. 2 shows the two lamella packets in cross section (I-I in FIG. 5b),

FIG. 3 is an enlarged detail (section line II-II in FIG. 2) of a lamellapacket with a riveted connection,

FIG. 4 is a schematic representation of a system to implement the methodaccording to the invention, and

FIG. 5 under a) and b) shows a top view onto a work holder used in thearrangement according to FIG. 4, with a packet of height lamellae and apacket of longitudinal lamellae.

METHODS FOR IMPLEMENTING THE INVENTION

FIG. 1 illustrates an arrangement of the above-described type. 10identifies the axis of a steering column, 20 a guide box, 30 and 40 twobearings for the steering column inside the guide box, 50 a partiallydepicted support strap fixed to the chassis and arranged bridge-likeover the guide box 20, and 60 and 70 two lamella packets. Lamella packet60 is fastened to support strap 50 by means of two eyes 65, 66 andlamella packet 70 to guide box 20 by means of two eyes 75 and 76. Acorresponding pair of lamella packets, not visible in FIG. 1, isarranged and fixed behind guide box 20 in the same manner as pair 60 and70. The lamellae of packet 60 have a vertically extending guide slot 67for adjusting the height of the steering column and are thereforereferred to as height lamella. A corresponding guide slot 77, butsubstantially horizontal, is also provided in the lamellae of packet 70and is used to adjust the steering column in longitudinal direction. Thelamellae of packet 70 are therefore referred to as longitudinallamellae. A tension bolt 80 that is held in the guide box penetrates theguide slots 67, 77 of lamella packets 60 and 70, that is to say of bothpairs in front of and behind guide box 20. When tension bolt 80 isloosened, the longitudinal lamellae, and with them, via guide box 20,the steering column can be displaced and pivoted in height and lengthrelative to the height lamellae and thus, via support strap 50, relativeto the chassis. The adjustment range is defined and limited by guideslots 67 and 77. The steering column can be locked in each desiredposition and pivot position of the adjustment range by tighteningtension bolt 80. This may be accomplished, for instance, by means of aschematically indicated locking lever 90. Tightening causes the frictionsurfaces of the lamellae to be pressed together.

FIG. 2 is a section along line I-I in FIG. 5b) through the two lamellapackets 60 and 70, shown here with four lamellae 61-64 and 71-74,respectively. In principle, there could also be only two or threelamella, or possibly more. Nor does the number of lamellae in the twopackets have to be the same. As may be seen, the individual lamellae61-64 and 71-74 of the two packets 60 and 70 are spaced apart at adistance that corresponds approximately to their thickness. Thus, thepackets can mesh such that a lamella of one packet is followed by alamella of the other packet in the stack. The mutual distance of thelamellae is defined and maintained by collars, which are formed on three(61-63 and 71-73) out of the four (61-64 and 71-74) lamellae of eachpacket, as shown in FIG. 2, along the edges of eyes 75 and 78 (as wellas 65 and 66). In the area of their mutual contact surfaces, thelamellae may be provided with some structuring, corrugation, or the like(78 in FIG. 1) to increase their mutual frictional resistance. Theuppermost lamella 61 of packet 60 is also provided with a trough-likeshaping 68 around guide slot 67, which serves as a guide for head 81 oftension bolt 80.

FIG. 3 shows the area of eye 75 of lamella packet 70 in cross section(II-II in FIG. 2). The aforementioned collars are clearly visible here.FIG. 3 further shows a rivet connection, which holds the lamella packet70 together. To form this rivet connection, the material of the lowestlamella 71 is pulled up far enough that it penetrates all the remaininglamellae 72-74 and can be shaped around the topmost lamella 74. Acorresponding rivet connection is provided in eye 66 of packet 60.

Due to the material deformation required to form the rivet connection,which can be quite substantial In part depending on the number oflamellae within the packet, the corresponding lamella, e.g. lamella 71,is made from a sheet metal material that is slightly softer and cantherefore be shaped more easily than the material used for the remaininglamellae. The latter material should be relatively hard so that theaforementioned corrugation or structuring of the friction surfaces isdurable. For this reason, the individual lamella packets each comprise asoft and one or more hard lamellae.

FIG. 4 shows a system for implementing the method according to theinvention, which permits efficient automatic production and assembly oflamella packets of the above-described type.

The system of FIG. 4 comprises two presses 110 and 120, a handlingstation 130, a packing station 140, and a conveyor system 150 connectingall these elements in a closed circuit. A plurality of work holders,only one of which is identified as 160, circulate within the-circuit inthe direction of the arrows. The first press 110 is supplied with anendless strip 111 of a relatively soft sheet metal material to producesoft lamellae and the second press with an endless strip of a relativelyhard sheet metal material 121 to produce hard lamellae.

In front of press 110 the work holders 160 are empty. At the ratedictated by the first press 110, one empty work holder 160 is introducedinto press 110, while another that has just been loaded is removedtherefrom and transported to the second press. In the first press 110,two soft lamella (a height lamella and a longitudinal lamella) arestamped in parallel from sheet metal material 111 and completely shapedincluding the collar for the aforementioned rivet connection in severalsequential steps (one step per cycle) by means of a so-calledprogressive die, and are placed side by side on the empty work holderpresent. Final separation from the strip takes place only in the laststep.

At the rate determined by the first press 110, a work holder carryingtwo soft lamellae side by side is introduced into the second press 120one station downstream, while another that has just been loaded isremoved therefrom and transported to the handling station 130. In thesecond press 120, essentially the same process takes place as in thefirst press 110, except that here hard lamellae are produced from theharder sheet metal material 121 and are placed onto the work holder overthe previously deposited soft lamellae. In the last step executed in thesecond press 120, the rivet connection is produced by shaping thecorresponding upwardly protruding collar on the soft lamella around thehard lamella.

If the lamella packets to be produced are intended to comprise severalhard lamellae, the second press 120 must be operated at acorrespondingly higher rate than the first press. A problem results fromthe fact that the hard lamellae of the same packet, as illustrated alsoin the example of FIG. 3, are shaped differently from one another,especially with respect to the spacer collar and possibly also withrespect to their structuring on the friction surfaces. This can beresolved, however, by using a controlled progressive die, which iscapable of executing different actions in the same position inconsecutive steps. Consequently, if several hard lamellae are used, thecollar on the soft lamella to produce the rivet connection can be shapedonly when the last hard lamella is placed on the stack and not before.

In handling station 130, the two lamella packets lying side by side onwork holders 160 as illustrated in FIG. 5a are pushed together intotheir functional position on work holders 160 as shown in FIG. 5b. Toaccomplish this without problems, a type of comb precisely determinesthe spacing of the lamellae.

In packing station 140, the lamella packets, which are pushed togetherin this manner in pairs and thereby save space, are finally transferredfrom the work holders 160 onto prepared blister pack holders 170. Asingle pack-holder can receive several lamella packets. The work holders160 are then free to pick up new lamellae in the first press 110.

What is claimed is:
 1. Method for producing lamella packets of the typetypically used in adjustable steering columns in automobiles, whichcomprise a soft lamella made of a relatively soft sheet metal materialand at least one hard lamella placed thereon and made of a relativelyhard sheet metal material, and in which the lamellae are connected by atleast one rivet formed, respectively, from the soft lamella,characterised by the use of two presses positioned to one after theother, wherein at the rate dictated by a first press; the soft lamellais completely formed and stamped from a strip of the relatively softsheet metal material in the first press; the soft lamella thus producedis transported to a second press; the hard lamella is completely formedand stamped from a strip of the harder sheet metal material in thesecond press, placed over the soft lamella, and the rivet connection isproduced.
 2. Method as claimed in claim 1, characterized in that thelamellae are produced in the presses in several steps, particularly byusing controlled progressive dies.
 3. Method as claimed in claim 1,characterized in that the second press is operated at a rate that isincreased by a multiple compared to the first press, for each cycle ofthe first press correspondingly more hard lamellae are produced andplaced on the soft lamella in the second press, and the rivet connectionis produced only with the last stroke of the second press.
 4. Method asclaimed in claim 1, characterized in that the lamellae are placed orstacked on mobile work holders in the presses and are transported onthese holders.
 5. Method as claimed in claim 4, characterized in thatthe work holders are operated in a closed cycle and prior to beingreturned to the first press are emptied by unloading the lamella packetsinto packing that is suitable for transport.
 6. Method as claimed inclaim 1, characterized in that the presses simultaneously produce heightlamellae and longitudinal lamellae side by side and rivet them to formheight lamella packets and longitudinal lamella packets, respectively.7. Method as claimed in claim 6, characterized in that thesimultaneously produced height lamella packets and longitudinal lamellapackets are brought into mutual engagement by pushing them together in astation downstream from the second press.
 8. Method as claimed in claim7, characterized in that a comb is used to define the mutual spacing ofthe height lamellae in the height lamella packets and the longitudinallamellae in the longitudinal lamella packets as the two packets arepushed together.